Process for making primed polymer surfaces and charge transfer media having conductivity sites thereon

ABSTRACT

The surface properties of solid substrates are improved by the formation of discrete sites of inorganic materials on one surface of the substrate.

TECHNICAL FIELD

The present invention relates to a novel method for forming novel primedpolymer surfaces and charge transfer media. Plasma treatment (eitherR.F., A.C. or D.C. generated) with an inorganic material present in theplasma causes a catalytic oxidation of the polymer surface to produce anoxygen enriched primed polymer surface. On a photoconductive insulatorsurface and a dielectric polymer surface, this produces conductivitysites which enhance the transfer of electrostatic charge from one suchsurface to another.

Over the past several decades, organic polymers have been extensivelyutilized to produce articles such as films, sheets, coatings, tapes orcloths, and are particularly desirable because of their superiorphysical and chemical properties in such areas as electricalcharacteristics, thermal characteristics, chemical resistance,flexibility and shatter resistance. However, since their surface isinert and insulative, they suffer from the shortcoming of low adhesionwhen it is desired to form composites with other materials such astoners, adhesives, paints, inks, etc., and electrostatic charge transferto such a surface is inefficient.

To improve the adhesion of such polymer surfaces for toners, adhesives,paints, inks, etc., prior art techniques have employed primer layers,chemical etching of the surface, physical roughening of the surface ofglow discharge. The latter of these techniques has more recentlyreceived greater utilization as improved glow discharge equipment, suchas R.F. and magnetron sputtering, has been developed. The R.F. andmagnetron sputtering techniques are particularly useful to microroughenand, hence, improve adhesion of low melting point dielectric materialssuch as polymers. Such techniques to improve adhesion of polymersurfaces are well known in the prior art.

It has been desirable to find a method of treating polymer surfaces tostill further enhance their adhesion and, thus, extend their utility informing composites with other materials. The present invention disclosesa method for oxidizing amorphous and crystalline polymeric material sothat the adhesion of the surface is significantly improved.

The transfer of latent electrostatic images from one surface to another,as for example, from an electrophotographic plate to a dielectricsurface, provides a method of electrostatic printing or copying freefrom the steps of plate and drum cleaning, thereby elminating the needfor cleaning devices, and consequently improving the life of plates anddrums and reducing the maintenance requirements. Processes known in theprior art for the transfer of electrostatic images (an art at timesreferred to by the acronym, TESI) have found practical application incommercial electrophotographic or electrostatic printing only for lowresolution images.

In electrophotography or electrostatic printing, the prior arttechniques for accomplishing charge transfer from one surface to anotherinvolves either: (1) conduction of electric charges across an air gap,or (2) direct charge transfer if the air gap is eliminated. While theair breakdown charge transfer technique is simple, it does not providehigh resolution (less than 80 line pairs per millimeters (lp/mm) can beachieved) or continuous tone gray scale reproduction. Finally, thismethod also requires the donor surface to sustain high surfacepotentials to insure air breakdown. The presently known techniques fordirect charge transfer require very smooth surface, a transfer liquidinterfacing the donor and receptor films, or very high pressures toeliminate the air gap. Even though high resolution of up to 150 lp/mmcharge transfer has been claimed, these techniques are impractical andthe charge transfer efficiency is generally low. Accordingly, thereremains a need for a simple means of making high resolution chargetransfer images with gray scale fidelity and high transfer efficiency.

One aspect of the invention is to disclose a process which can providean efficient charge donating photoconductive-insulative surface.

Another aspect of the invention is to produce materials which canefficiently transfer a high resolution latent electrostatic charge imagefrom the charge donating photoconductive-insulative surface to thecharge receptor medium while these surfaces are in virtual contact.

One other aspect of the present invention is to disclose a process whichcan provide a process for improving the adhesion of polymer surfaces.

A further aspect of the present invention is to provide a method foroxidizing polymer surfaces using a metal catalyst and anoxygen-containing plasma.

A further aspect of the present invention is to disclose a process whichcan provide an improved primed polymer surface, particularly forpressure sensitive acrylics and for hot melt copolyester adhesives.

A further aspect of the present invention is to provide a method ofpriming polymer surfaces which is both efficient and pollution-free.

BACKGROUND ART

It is conventional practice in many different areas of technology toimprove the bonding capability of surfaces by treating them in onefashion or another. This treatment, in all of its various forms, isgenerally called priming. The most common methods of priming surfacesinclude the application of an intermediate layer, physically rougheningthe substrate, chemically modifying the substrate (e.g., oxidation), andcombinations of these methods. With advances in related technologies,each of these methods may be formed by more efficient procedures, butgenerally accomplish similar effects. For example, in a physicalroughening process, the use of such different procedures such as dryabrasive grit, rotary brushes, abrasive grain slurries, and otherssimilar techniques produce similar effects with their own slightvariations in properties.

U.S. Pat. Nos. 4,064,030 and 4,155,826 show that radio frequency (R.F.)sputter-etching of fluorinated olefin polymer surfaces provide improvedadhesion for other coating materials without the discoloration attendantalkali etching. The sputter-etching is also stated to be more effectivethan physical roughening or glow discharge to effect priming.

U.S. Pat. No. 3,018,189 shows the use of electrical discharges to modifythe surface of a polymer to improve the adhesion of other materials toit.

The deposition of metal oxide coatings onto polymer surfaces to improveadhesion by a cathodic deposition from a solution of isopropanol and anitrate salt is shown in U.S. Pat. No. 4,094,750.

U.S. Pat. No. 3,852,151 discloses the use of a discontinuous particleadhesion promoting layer of metal, glass, mineral or ceramic sphericalparticles having diamters of from 10 to 100 micrometers.

Chemical oxidation of polymer surfaces is also generally well known inthe art as represented by U.S. Pat. Nos. 3,418,066 and 3,837,798.

The formation of metal-oxygen-polymer complexes at the surface of metalvapor coated, oxygen plasma treated polymeric materials has been notedas improving adhesion between the metal and the polymer (J. Vac. Sci.Technol., J. M. Burkstrand, 16(4) July/August 1979). The effects ofimproved adhesion by plasma treatment of polymer surfaces is well knownin the art (J. Pol. Sci., `ESCA Study of Polymer Surfaces Treated byPlasma,` H. Yasuda et al., (1977) Vol. 15, pp. 991-1019), and (J. Affl.Phys., `Metal-polymer Interfaces`, J. M. Burkstrand, (1981) 52 (7), pp.4795-4800).

Ion sputtering to texture polymeric and metal surfaces is anotheravailale technique used to improve the adhesion to surfaces (NASATechnical Memoranda 79000 and 79004, Sovery and Mirtich et al.,Technical paper present to 25th National Vacuum Symposium Nov. 28-Dec.1, 1978).

Metal layers have also been sputtered onto electrophotographic films ina thickness of 0.7 to 4.0 mm in order to reduce visible lighttransmission as shown in U.K. Pat. No. 1,417,628.

SUMMARY OF THE INVENTION

The present invention discloses an improved method of, and means for,priming polymeric surfaces and particularly for forming novelelectrostatic charge transfer surfaces. Photoconductive insulators anddielectrics are provided with a multitude of conductivity sites togenerate unique electrostatic charge donors and electrostatic chargereceptors, respectively, which are then utilized to provide anefficient, high resolution means of tranferring and developingelectrostatic charge patterns. The inventive method comprises treating apolymer surface with an atmosphere of inorganic atomic or molecularmaterial which is solid at 30° C. The atmosphere may be an inert orreactive plasma (R.F., A.C. or D.C. sputter generated or thermallyevaporated) with or without an additional reactive material or elementpresent in the plasma so that a deposition on the polymer surfaceoccurs. Where the reactive plasma is an oxidizing plasma, such asoxygen, with metal containing species therein, a mediated oxidationoccurs at the polymer-sputter deposited layer which providesoxygen-enriched polymer surface.

DETAILED DESCRIPTION AND SPECIFICATION OF THE INVENTION

According to the invention, the surfaces of a photoconductive insulatorand a dielectric or a polymer such as polyester are treated to provide amultitude of conductivity sites or priming sites. Conductivity siteswere produced by the R.F., A.C. or D.C. sputter deposition of anyinorganic material. It is preferred to use an inorganic material havinga bulk resistivity of less than 1×10¹⁸ ohm-cm and more preferably amaterial having a bulk resistivity of less than or equal to 1×10¹²ohm-centimeters in an inert (e.g., Ar) or reactive (e.g., O₂ or CO₂) gasenvironment or by thermal evaporation including electron beamevaporation of a metal or metal oxide at pressures less than thattypically used in sputter deposition. Priming sites were identicallyproduced, generally using a reactive environment, such as with areactive gaseous environment,. It should be understood that othermetal-containing materials such as semiconductors could be used for thedeposition material as primers or conductivity sites. The sputterdeposition technique was particularly suited to maintainiag a uniformsize and distribution of conductivity sites over the entire surface.Particularly useful articles provided by this process include animproved electrostatic charge receptor and an improved electrostaticphotoconductive-insulative charge donor. The resultant importantperformance improvement of these articles according to this inventionresides in the increased electrostatic charge transfer efficiencybetween the two surfaces when they are brought into contact between thetwo surfaces on which conductivity sites exist. An additional, and justas important, improvement is that the efficient charge transfer isaccomplished without an electrical bias; that is, the conductivityplanes of the charge receptor and charge donor, respectively, need onlybe brought to the same electrical potential, which preferably is groundpotential.

The general objective of the process is to produce a surface havingdiscrete conductivity sites thereon. These conductivity sites shouldhave a defined average size range (measured along the plane of thesurface) of between about 2.5 and 9.0 nanometers. The distribution canbe quite large, however. For example, when the average size is about 7.0nm, the range in particle sizes can be from 5 to 12.0 nm, or even have agreater size distribution. The average particle size does appear to becritical to the practice of the invention even though the distributionmay be broad. The distribution tends to be a result of the variousprocesses of manufacture, however, and a broad distribution range isneither essential nor necessarily desirable. The broad average sizerange appears to be from 1.0 to 20 nm. The preferred range is from 2.5to 9.0 nm. The more preferred range is from 3.0 to 8.0 nm, and the mostpreferred average sizes are between 3.5 and 7.5 nm.

In addition to the criticality of the average particle size of theconductivity sites, the spacing of the sites should be within reasonablelimits. The sites should cover between 0.1 to 40% of the surface area,preferably 0.15 to 30%, and more preferably 0.20 to 20% of the surfacearea. If more area is covered, the surface essentially becomes aconductor. If less area is covered, the effects of the sites tend to notbe noticeable.

Essentially any solid, environmentally stable inorganic material may beused as the composition of the conductivity sites. By environmentallystable it is meant that the material, in particulate form of from 2.5 to9.0 nm, in air at room temperature and 30% relative humidity will notevaporate or react with the ambient environment to form anon-environmentally stable material, within one minute. Metal particlescan be deposited and, if these react to form environmentally stablemetal oxide particles, are acceptable. Copper and nickel perform thisway, for example. Metals which react to form unstable products withinthat time period, e.g., metal oxides which sublime or are liquld, wouldnot be suitable. Surprisingly it has been found that the beneficialeffect of the sites appears to be solely a function of conductivity sitedensity and is independent of the bulk resistivity properties of thecomposition. For example, silica (SIO₂), alumina, chromia and all otherinorganics tested have been found to be quite effective in increasingthe charge acceptance characteristics of the surface even though it isan insulator. Essentially all environmentally stable materials havingthe described average particle size and distribution work in the presentinvention. Specific materials used include nickel, zinc, copper, silver,cobalt, indium, chromium/nickel alloy, stainless steel, aluminum, tin,chromium, manganese, quartz, window glass, and silica. Oxides of thesematerials and mixtures of metals and metal oxides of these materialsalso work quite well. It is apparent that sulfides, carbonates, halides,and other molecules of metals and the like also work in the presentinvention.

The conductivity sites may be deposited on the surface by a number ofdifferent processes, including but not limited to radio frequency (R.F.)sputtering, vapor deposition, chemical vapor deposition, thermalevaporation, A.C. sputtering, D.C. sputtering, electroless deposition,drying of sols, and drying in dilute solutions of the metal orcompounds. The objective of all these processes is the distribution ofcontrolled size particles. This is achievable in these processes bycontrol of the speed, concentration of ingredients, and energy levelsused. In almost all cases atomic or molecular size material is contactedwith the surface and these materials tend to collect at nucleation sitesor minute flaws in the surface. As the particles grow by attraction andaccumulation of additional material, the process is carefully controlledto insure that the proper size and distribution of particles iseffected. These procedures would be readily understood by one ofordinary skill in the art.

The process of the present invention comprises the process of forming anatomic or molecular atmosphere of the material to be deposited andallowing the elements and/or molecules to deposit on the surface whichis to be coated at a rate and for a time sufficient to form the desireddistribution of sites. This process can be done on existing thermalevaporation (also known as vapor coating) apparatus and sputteringapparatus. No modification of existing apparatus is essential inpracticing this process, but care must of course be exercised that theappropriate concentration and distribution of sites be obtained. Forexample, if the surface to be coated is exposed to an atmosphere with ahigh concentration of metal or metal oxide for too great a time, a filmwould be deposited rather than a distribution of sites.

The process of the present invention, using R.F., A.C. or D.C.sputtering and thermal evaporation has to date been the best process forproviding consistent results and for ready control of properties.

The effectiveness of the process for making charge receptive surfacescan be determined in a simple test. A control electrophotographic sheetcomprising the sheet of Example 1 is charged to 450 volts. The chargesurface of this sheet is contacted by the treated surface of the presentinvention. If at least 25% of the charge on the sheet is transferredwithin five seconds of contact, the material selected is clearlysatisfactory.

A preferred utility of the present invention to provide a primed surfaceexhibiting enhanced adhesion is accomplished when a metal or metal oxideis selected as the material for producing the conductivity sites, apolymer such as polyester is selected as dielectric substrate and R.F.sputter deposition is carried out in a reactive oxygen atmosphere. Thepolymer surface is considered primed if it passes the adhesive tape peeltest, ANSI/ASTM D 903-49 (reaffirmed 1978). This test consists ofplacing a piece of Scotch Brand Magic Mending Tape onto the treatedsurface and pressing it down to obtain firm adherence. Subsequently, thetape is peeled at moderate speeds (approximately 50 cm/min). A surfacethat is primed shows a uniform splitting of the adhesive from the tapebacking.

Objects and advantages of this invention are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as the conditions and details, shouldnot be construed to unduly limit this invention.

EXAMPLE 1

A charge receptor was fabricated by selecting as a substrate a 15 cmlong×10 cm wide piece of 75μ thick polyester. Upon the substrate wasvacuum vapor deposited (i.e., thermally evaporated) an aluminum metallayer which had a white light transparency of about 60 percent and aresistance of about 90 ohms/square. Subsequently, a dielectric layer washand coated from a 15 wt. % Vitel® PE 200 (polyester from Goodyear Tireand Rubber Co., Ohio, Chemical Division)/85 wt. % dichloroethan solutionusing a #20 Meyer bar which resulted in dried thickness of about 5μ.Further processing was done in a Veeco® Model 776 radio frequency diodesputtering apparatus operating at a frequency of 13.56 MHz, modified toinclude a variable impedence matching network. The apparatus includedtwo substantially parallel shielded circular aluminum electrodes, one ofwhich (cathode) was 40 cm in diameter and the other (anode) was 20 cm indiameter with a 6.25 cm gap between them. The electrodes were housed ina glass jar provided with R.F. shielding. The bell jar was evacuatableand the cathode (driven electrode) and anode (floating electrode) werecooled by circulating water.

The foregoing composite was centrally placed on the aluminum anode withthe dielectric layer facing the cathode. The source of the material tobe sputter deposited was a copper plate, which plate was attached to thecathode thus facing the composite structure on the anode.

The system was then evacuated to about 1×10⁻⁵ torr, and oxygen gasintroduced through a needle valve. An equilibrium pressure in the rangeof 5×10⁻⁴ torr to 8×10⁻⁴ torr was maintained as oxygen was continuouslyintroduced and pumped through the system.

With a shutter shielding the anode and composite structure thereon, R.F.energy was capacitively coupled to the cathode, initiating a plasma. Theenergy input was increased until a cathode power density of 0.38watts/cm² was reached, thus causng copper to be sputtered from thecathode and deposited on the shutter. This cathode cleaning operationwas carried on for about ten minutes to assure a consistent sputteringsurface. The cathode power was then reduced to 0.15 watts/cm² and thesputtering rate was allowed to become constant as determined by a quartzcrystal monitor. A typical sputtering rate was nominally 0.1 nm/60seconds. The shutter was then opened and the reactive sputter depositionof copper metal onto the dielectric layer was continued for about 60seconds. Reflected power was less than 2 percent. The couplingcapacitance maintained the above stated power density. In 60 seconds,the average film thickness was, therefore, approximately 0.1 nm. Acharge receptor surface consisting of copper or copper oxideconductivity sites having a median size of about 7.0 nm and an averagespacing of about 20 nm was thus formed.

A charge donor material was treated in a similar manner. However, thecomposite structure consisted of a 75μ thick polyester layer covered bya conductive indium iodide layer, which in turn was covered by an 8.5μthick organic photoconductive-insulative layer commercially availablefrom Eastman Kodak Company as EK SO-102, in the R.F. sputteringapparatus discussed above with the exception that the material depositedwas 304 stainless steel. The average thickness of the stainless steeldeposited was nominally 0.05 nm and formed a distribution ofconductivity sites on the surface of the photoconductive-insulationlayer.

The photoconductive-insulator layer used above (EK SO-102) comprises amixture of (1) a polyester binder derived from terephthalic acid,ethylene glycol and 2,2-bis(4-hydroxyethoxyphenyl)propane, (2) a chargetransport material comprisingbis(4-diethylamino-2-methyl-phenyl)phenylmethane, and (3) a spectralsensitizing dye absorbing at green and red wavelengths combined with asupersensitizer.

The charge donor was then charged to +900 volts using a corona sourceand image-wise exposed to generate a high resolution electrostaticcharge pattern. With the electrostatic charge pattern on its surface,the charge donor was then brought into intimate contact with a chargereceptor using a grounded electrically conductive rubber roller. Theroller provides electrical contact to the back electrode for the chargereceptor as well as providing the moderate pressure needed for goodcontact. Measurement of the surface potential on the charge receptorafter separation from charge donor indicated that about 50% of theelectrostatic charge transferred. The transferred electrostatic chargepattern was then stored as long as several days and subsequentlydeveloped, or developed immediately with toner to reveal a visible imageof the charge pattern.

A suitable toner for developement of the transferred electrostaticcharge was composed as shown in Table I.

                  TABLE I                                                         ______________________________________                                                        Proportions                                                                             % Composition                                       Raw Material    by weight by weight                                           ______________________________________                                        Tintacarb 300.sup.(a)                                                                         2         10.5                                                Polyethylene Ac-6.sup.(b)                                                                     1         5.3                                                 OLOA 1200.sup.(c)                                                                             4         21.0                                                Isopar M.sup.(d)                                                                              12        63.2                                                                          100.0                                               ______________________________________                                         .sup.(a) Tintacarb 300 Carbon Black manufactured by Australian Carbon         Black, Altona, Victoria, Australia                                            .sup.(b) Polyethylene AC6, low molecular weight polyethylene maufactured      by Allied Chemicals, New York                                                 .sup.(c) OLOA 1200, an oil soluble succinimide manufactured by the Chevro     Chemical Company, San Francisco, California                                   .sup.(d) Isopar M, Isoparaffinic hydrocarbon, high boiling point,             manufactured by Exxon Corp.                                              

The toner components were mixed according to the following sequence:

1. The carbon black was weighed and added to a ball jar.

2. The Polyethylene AC-6, OLOA 1200 and Isopar M were weighed into acommon container, preferably a glass beaker, and the mixture heated on ahotplate with stirring until solution occurred. A temperature of 110°C.±10° C. was sufficient to melt the polyethylene and a clear brownsolution was obtained.

3. The solution from (2) was allowed to cool slowly to ambienttemperature, preferably around 20° C., in an undisturbed area. The waxprecipitated upon cooling, and the cool opaque brown slurry so formedwas added to the ball jar.

4. The ball jar was sealed, and rotated at 70-75 rpm for 120 hours. Thismilling time was for a jar of 2600 mL nominal capacity, with an internaldiameter of 18 cm. A jar of these dimensions would take a total chargeof 475 g of raw materials, in the proportions stated in Table I.

5. Upon completion of the milling time, the jar was emptied and thecontents placed in a suitable capacity container to form the final tonerconcentrate designated MNB-2.

The resultant image was of excellent quality wherein the optical densitywas about 1.4, the resolution was about 216 lp/mm and the slope (γ) inthe linear portion of optical density as a function of log exposure wasabout 1.1.

COMPARATIVE EXAMPLE 1

A charge receptor and a charge donor were prepared as in Example 1,however, no conductivity sites were deposited on either of the articles.When the image-wise exposure, electrostatic charge image transfer andtransferred charge development were carried out as in Example 1, onlyabout 9% of the electrostatic charge transferred and the resolution ofthe developed image was only about 100 lp/mm.

COMPARATIVE EXAMPLE 2

A charge receptor and a charge donor were prepared as in Example 1,however, no conductivity sites were deposited on the charge receptor.When the image-wise exposure, electrostatic charge image transfer andtransferred charge development were carried out as in Example 1, onlyabout 28% of the electrostatic charge transferred and the resolution ofthe developed image was only about 150 lp/mm.

COMPARATIVE EXAMPLE 3

A charge receptor and a charge donor were prepared as in Example 1,however, no conductivity sites were deposited on the charge donor. Whenthe image-wise exposure, electrostatic charge image transfer andtransferred charge development were carried out as in Example 1, onlyabout 39% of the electrostatic charge transferred and the resolution ofthe development image was only about 170 lp/mm.

EXAMPLES 2-14

Electrostatic charge image patterns were generated, transferred anddeveloped as in Example 1 with the exception that chromium (Cr), silver(Ag), tin (Sn), cobalt (Co), manganese (Mn), nickel (Ni), iron (Fe),molybdenum (Mo), stainless steel, zinc (Zn), aluminum (Al), window glassand quartz were used respectively to generate the conductivity sites onthe charge receptor. Results obtained thus far indicate charge transferefficiencies in excess of 30% and developed resolutions greater than 170lp/mm for all these examples. Comparable satisfactory results were alsoobtained with sites formed by sputtering in argon and carbon dioxideatmospheres.

The utility of the present invention in providing a primed surfaceexhibiting enhanced adhesion is demonstrated in the following additionalexamples.

EXAMPLE 15

A 12.5 cm×25.0 cm piece of 75μ thick polyester was selected as thesubstrate. The R.F. sputtering apparatus of Example 1 was utilized withthe exception that the anode was 40 cm in diameter. The substrate wasplaced on the anode, the chamber evacuated and an equilibrium pressurein the range of 5×10⁻⁴ torr to 10×10⁻⁴ torr of oxygen was maintained.Copper was sputtered at a cathode power in the range of 0.38 watts/cm²to 0.46 watts/cm². The deposition was stopped when about 0.5 nm ofcopper had been deposited.

The primed surface so prepared was subjected to the adhesion peel testdescribed above and an uniform splitting of the adhesive from the tapebacking occurred.

EXAMPLE 16

A 12.5 cm×25.0 cm piece of Tedlar® (polyvinylfluoride) was selected asthe substrate and treated as in Example 15. It, too, passed the adhesiontape peel test.

EXAMPLE 17

A 12.5 cm×25.0 cm piece of polyethylene was selected as the substate andtreated as in Example 15. The surface so primed passed the adhesion tapepeel test. Substantially identical results were obtained usingpolypropylene as the substrate.

EXAMPLE 18

Continuous R.F. reactive sputter treatment was also utilized to primepolymer surfaces. A 15 cm wide roll of polybutyleneterephthalate (PBT)was loaded on a web handling apparatus and inserted into the vacuumchamber of a planar magnetron sputtering system. The vacuum chamber wasevacuated to approximately 5×10⁻⁶ torr and oxygen admitted to obtain aflow rate of 54 standard cc/min with a chamber pressure in the range of10×10⁻³ torr to 25×10⁻³ torr. The web was passed by a copper planarmagnetron sputter deposition cathode at a rate of 0.1 to 2 cm/sec. Thecathode to web spacing was 6 cm. The gas plasma was formed by drivingthe cathode by a radio frequency (13.56 MHz) generator at a power in therange of 1.1 watts/cm² to 3.4 watts/cm².

The surface so primed passed the adhesion tape peel test.

EXAMPLE 19

A 15 cm wide roll of single layer 60/40 copolymer ofpolyethyleneterephthalate and polyethyleneisophthalate was treated as inExample 18. The surface so primed passed the adhesion tape peel test.

EXAMPLES 20-21

The materials of Examples 18 and 19 were primed as in Example 18 withthe exception that the planar magnetron sputter deposition cathode waschromium. These primed surfaces passed the adhesion tape peel test andwere particularly stable in humid environments.

EXAMPLES 22-23

The materials of Examples 18 and 19 were primed as in Example 18 withthe exception that the planar magnetron sputter deposition cathode wasaluminum and the gas plasma was formed by driving the cathode by adirect current (D.C.) generator at a power in the range of 1.1 watts/cm²to 1.3 watts/cm².

The surfaces so primed passed the adhesion tape peel test.

An ESCA (electron spectroscopy for chemical analysis) study of surfacesof polymers that were treated under plasma conditions, as disclosed inthe examples, was conducted. A determination of properties andconditions that resulted in priming versus conditions and propertieswhich did not result in priming was sought. In the case of priming withchromium, which is preferred in this disclosure, the Cr 2p^(3/2) bindingenergy for primed surfaces was 576.6 ev, whereas the Cr 2p^(3/2) bindingenergy for unprimed surfaces was 577.1 ev. In the case of priming withaluminum, the Al 2s binding energy for primed surfaces was 119.0 ev,whereas the Al 2s binding energy for unprimed surfaces was 119.3 ev. Allbinding energies are referenced to C 1s which is at 284.6 ev. It hasbeen found that binding energies are a function of preparationconditions and not of average deposited metal thickness as reported byBurkstrand, supra.

The materials primed as disclosed above were found particularly usefulin forming composite structures with pressure sensitive acrylic, and hotmelt segmented copolyester adhesives.

EXAMPLE 24

A 4 inch×6 inch (approximately 10 cm×15 cm) sample of polyester with avapor deposited film of aluminum (60% transmissive) as a conductivelayer thereon was coated with 5 micrometers of polyester (Vitel® PE200). This film composite was placed in a vacuum chamber equipped with athermal evaporation assembly and a shutter. The composite was placedapproximately 20 cm above the source of material to be deposited. Thesystem was evaporated to 1-2×10⁻⁵ torr and, with the shutter closed,power was applied to the copper filled tungsten support boat. When thedeposition rate was constant, as evidenced by readings from a thicknessmonitor, the shutter was opened and 0.1 nanometers of copper wasdeposited. The 0.1 nanometer coated sample was tested according to thesame procedures used in Example 1 and was found to provide transferredresolution after development of greater than 100 lp/mm.

EXAMPLE 25

A charge receptor was prepared as in Example 1 with the exception thatgold (Au) was used as the metal in forming the conductive sites. Thecharge donor was a plain cadmium sulfide crystalline photoreceptorcommercially available from Coulter Systems Company as KC101. Afterimage-wise exposure, electrostatic charge transfer and transferredcharge development were carried out according to the method of Example1, the developed image had a resolution of 130 lp/mm. About 4.0% of thecharge had been transferred.

The imaging and developing process was repeated on an identical receptorwithout conductivity sites and no image could be produced, and no chargetransfer could be detected.

EXAMPLE 26

The previous example was repeated except that the photoreceptorcomprised a 1.59 mm thick aluminum blanket covered by a 40 micrometeramorphous composition comprising 94% by weight selenium and 6% by weighttellurium. Resolution of the developed image was 120 lp/mm. About 40% ofthe charge had been transferred during the process.

Metalloids are equally useful in the practice of the present inventionin place of or in combination with the metals and metal compoundsdescribed above. Metal alloys, metal-metalloid alloys, and metalloidalloys are also useful and can be applied as discrete sites according tothe procedures described above. Metalloids are elements well understoodin the art and include, for example, silicon, boron, arsenic, germanium,gallium, tellurium, selenium and the like. The metalloids, in the samefashion as the metals, may be present in the form of metalloidcompounds. The terms "metal compounds" and "metalloid compounds" aredefined according to the present invention to mean oxides, chalconides(e.g., sulfides), halides, borides, arsenides, antimonides, carbides,nitrides, silicides, carbonates, sulfates, phosphates, cluster compoundsof metals and metalloids, and combinations thereof.

Terms such as `oxides` are not limited to exact stoichiometricequivalence. Materials with either an excess or deficiency ofstoichiometric oxygen are useful and can be produced according to thetechniques above. Sputtering of silica in an inert atmosphere tends toproduce a sub-oxide, for example.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

We claim:
 1. A process for improving the surface properties of a solidsubstrate by increasing the electrostatic charge transfer efficiency ofthe surface or by increasing its priming according to ANSI/ASTM D 903-49consisting essentially of depositing a material different from that ofthe substrate and having a bulk resistivity of less than 1×10¹⁸ ohm-cmonto at least one surface of a solid substrate by a process selectedfrom the group consisting of radio frequency sputtering, vapordeposition, chemical vapor deposition, thermal evaporation, A.C.sputtering, D.C. sputtering, electroless deposition and drying of gelsso as to form uncoated discrete sites of an inorganic material on saidat least one surface, said discrete sites having average length ofbetween 1.0 and 20.0 nm and covering between 0.1 and 40% of saidsurface.
 2. The process of claim 1 wherein said material is anenvironmentally stable material selected from the group consisting ofmetals, metalloids, metal compounds, metalloid compounds, andcombinations thereof.
 3. The process of claim 2 wherein the sites haveaverage lengths of between 2.5 and 9.0 nm and covering 0.15 to 30% ofsaid surface.
 4. The process of claims 2 or 3 wherein said materialcomprises metal and said sites comprise metal, metal oxide or mixturesthereof.
 5. The process of claims 2 or 3 wherein said material comprisesat least one metal oxide and said sites comprise metal oxide.
 6. Theprocess of claims 2 or 3 wherein said material comprises a mixture ofmetal and metal oxides.
 7. The process of claims 2 or 3 wherein saidsites have an average length measured along the plane of the surface ofbetween 3.0 and 8.0 nm and said material comprises metal, metal oxide orcombinations thereof.
 8. The process of claims 1 or 2 wherein saidsubstrate is an organic polymeric material.
 9. The process of claim 7wherein said substrate is an organic polymeric material.
 10. The processof claim 2 wherein the surface of said substrate comprises an organicphotoconductive-insulator layer.
 11. A process for improving the surfaceproperties of a solid substrate by increasing the electrostatic chargetransfer efficiency of the surface or by increasing its primingaccording to ANSI/ASTM D 903-49 consisting essentially of depositing amaterial different from that of the substrate and having a bulkresistivity of less than 1×10¹⁸ ohm-cm onto an organicphotoconductor-insulator layer which forms at least one surface of solidsubstrate by a process selected from the group consisting of radiofrequency sputtering, vapor deposition, chemical vapor deposition,thermal evaporation, A.C. sputtering, D.C. sputtering, electrolessdeposition and drying of gels so as to form uncoated discrete sites ofan inorganic material on said at least one surface, said discrete siteshaving average length of between 1.0 and 20.0 nm and covering between0.1 and 40% of said surface.
 12. The process of claim 11 wherein saidmaterial is an environmentally stable material selected from the groupconsisting of metals, metalloids, metal compounds, metalloid compoundsand combinations thereof.
 13. The process of claim 12 wherein said thesites have average lengths of between 2.5 and 9.0 nm and covering 0.15to 30% of said surface.
 14. The process of claim 13 wherein said siteshave an average length measured along the plane of the surface ofbetween 3.0 and 8.0 nm and said material comprises metal, metal oxide orcombinations thereof.